The Urinary System

1. The Urinary System Structure & Function

2. Anatomy of the Urinary system • 2 - Kidneys • 2 - Ureters • 2 - Renal arteries • 2 – Renal veins • 1 - Urinary bladder • 1 - Urethra

3. The Kidneys • Two bean shaped kidneys 4-6 ozs. each, found in the retroperitoneal cavity. • Filter wastes from blood, and maintain water & electrolyte balance. • Fist sized • Protected by adipose tissue and fibrous connective tissue

4. Structures of the kidney • Renal Pelvis: a basin like are in the central part of kidney • Renal Cortex: outer layer of kidney containing nephrons • Nephrons are the functional units of the kidney. • Medulla: Inner layer containing urine collecting tubules

5. Nephrons • Each nephrons forms urine by the processes of filtration, reabsorption and secretion • Each contains a glomerulus, which is a cluster of capillaries, surrounded by a membrane called the Bowman’s capsule

6. The Ureters • Ureters- slender tube carries urine from renal pelvis/kidneys to bladder. • 15-18 in. long • Urine enters the tube every 10-30 seconds in spurts due to peristaltic activity • Ureteral orifice at bladder prevents reflux

7. The Bladder and Urethra • Bladder- muscle sac that receives and stores urine. • Lined with ruggae • Stores 250 cc (about 1 pint) of urine • Urethra- slender tube carries urine from bladder outside body. • Female: 1-1.5 in. • Male: 8 in. long (in the male, the urethra conveys both urine and semen, Neck of the urethra is surrounded by the prostrate gland) • Urethral meatus – external opening of the urethra

8. Main Function of the Urinary System • Remove urea (nitrogenous waste) from the blood stream so that it does not accumulate in the body and become toxic • Urea: formed in liver from ammonia (from breakdown of simple proteins, amino acids, in the body cells) • Urea carried by the blood stream to the kidneys for excretion.

9. Other functions • Maintain proper balance of water, salts and acids • Example: Na and K which are electrolytes needed for proper functioning of muscle cells. • Kidneys can adjust what is excreted or held back • Kidneys also act as an endocrine organ as they secrete renin, which controls blood pressure • Help with calcium reabsorption in the intestines • Extract insulin and parathyroid hormone from the blood stream

10. How do kidneys produce urine? • Blood from the aorta branches into the Rt. And Lt. Renal artery • The arteries branch into arterioles throughout the renal cortex • Blood flow is slow and constant • If the blood flow diminishes the kidneys would produce renin, which stimulates contraction of the arterioles, increased BP and blood flow will be restored!

11. Continued… • In each cortex, blood passes through the glomerulus and water, salt, sugar and urea are filtered out of the bloodstream. • This waste is collected in the Bowman’s Capsule and transported to the renal tubule. • In the renal tubule, reabsorption of needed substances and secretion of waste products is completed. • It is now urine, 95% water and 5% waste substances . • The tubules lead to the renal pelvis, which narrows to the ureter, then the bladder and excreted out of the urethra! • Sphincters hold urine until desire to urinate.

12. Urine • 95% water • 5% waste, toxins and salts • Clear, pale amber • 1000cc – 2000cc excreted every 24 hours • Urochrome is the pigment that gives urine its normal yellow color

13. Facts • The acid found in urine gives off that typical urine smell. In diabetics, urine may smell fruity due to the presence of glucose.Freshly made urine from the kidney is sterile but when it leaves the body, it is exposed to bacteria present in the surrounding skin.A bacterial invasion leads to a breakdown of the salts in the urine to give off a foul-smelling odor. If urine smells offensive the minute urination starts then there is already an infection in the urinary tract.